CN102148280A - Novel silicon substrate heterojunction solar cell - Google Patents

Abstract

The invention discloses a novel silicon substrate heterojunction solar cell. An Ag back electrode is formed on the back surface of an N-type monocrystalline silicon or polycrystalline silicon slice through evaporation; intrinsic amorphous silicon (i-a-Si:H), P-type nanosilicon (p-nc-Si:H), P-type heavily doped amorphous silicon (p+-a-Si:H) and ultrathin intrinsic amorphous silicon (i-a-Si:H) are deposited on the front surface (light receiving surface of a cell) of the silicon slice in sequence; finally an ITO (Indium Tin Oxide) transparent conductive thin film is sputtered on the silicon; and an Ag gate line electrode is printed by a screen. The solar cell with the novel structure has lower cost than that of the normal silicon solar cell, so that the light-induced degradation of the normal amorphous silicon solar cell is reduced, and the cell has higher stability in long-term use, high light absorbing capacity and high photoelectric conversion efficiency. The efficiency reaches 17.2 percent at the standard analog light intensity of AM1.5, 100mW/cm<2>.

Description

A new type of silicon substrate heterojunction solar cell

technical field

The invention relates to the technical field of semiconductor solar cells, in particular to a silicon-based heterojunction solar cell structure.

Background technique

At present, in the international market, crystalline silicon and polycrystalline silicon solar cells occupy a leading position in the market due to their high conversion efficiency and mature production technology. However, the high temperature (above 900°C) diffusion junction process used in the production of these traditional silicon solar cells consumes a lot of energy, so the production cost is high. With the development of photovoltaic industry technology, it is necessary to adopt new technologies and methods to prepare solar cells to reduce Production costs and further improvement of conversion efficiency, thereby opening up a wider market.

The production of thin-film solar cells by low-temperature thin-film preparation technology is a new direction of solar cell research. It saves expensive material costs, reduces energy consumption, and has a simple production process, which is easy for large-scale continuous production and is conducive to reducing manufacturing costs. However, the problem of photodegradation of hydrogenated amorphous silicon (a-Si:H) solar cells has not been well resolved, and its photoelectric conversion efficiency is low.

To solve these problems, a feasible way is to use wide-bandgap a-Si as the window layer or emitter, and single-crystal silicon or polycrystalline silicon wafers as substrates to form heterojunction solar cells, which utilize the wide-bandgap hydrogenated amorphous silicon And the advantages of high photoconductivity and good stability of crystalline silicon avoid the light-induced attenuation of solar cell performance caused by the instability of amorphous silicon. This kind of battery not only utilizes the advantages of thin-film manufacturing technology, but also takes advantage of the material performance characteristics of crystalline silicon and amorphous silicon, and has the development prospect of realizing high-efficiency and low-cost silicon solar cells.

Contents of the invention

In order to solve the shortcomings of crystalline silicon solar cells and amorphous silicon solar cells, the technical problem to be solved by the present invention is to propose a new type of solar cell with strong light absorption ability, high efficiency and low cost in combination with the performance characteristics of single crystal silicon and amorphous silicon materials. Silicon based heterojunction solar cells.

The novel silicon-based heterojunction solar cell provided by the present invention to solve the above-mentioned technical problems comprises Ag grid line electrodes, transparent conductive films (ITO), intrinsic amorphous silicon layers (ia-Si:H), P-type heavily doped Doped amorphous silicon layer (p ⁺ -a-Si:H), P-type nano-silicon layer (p-nc-Si:H), intrinsic amorphous silicon layer (ia-Si:H), N-type silicon Substrate and Ag metal back electrode, wherein:

The Ag grid line electrode is located on the transparent conductive film ITO, and its function is to serve as the front-side lead-out electrode;

A transparent conductive film is located on the intrinsic amorphous silicon layer as the front electrode;

The intrinsic amorphous silicon layer is located on the P-type heavily doped amorphous silicon layer, and its function is to passivate the surface of the P-type heavily doped amorphous silicon layer to make it better in contact with ITO;

The P-type heavily doped amorphous silicon layer is located on the P-type nano-silicon layer, and its function is to form a p ⁺ /p tunnel junction and form a good ohmic contact;

The P-type nano-silicon layer is located on the intrinsic amorphous silicon layer and the N-type silicon substrate, and its function is to form a p-n heterojunction with the N-type silicon substrate to generate the photovoltaic effect;

The intrinsic amorphous silicon layer is located on the N-type silicon substrate, and its function is to passivate the silicon surface and reduce the interface state density;

The N-type silicon substrate is located on the Ag metal back electrode, which acts as the base area of the solar cell;

The Ag metal back electrode is used as the back lead-out electrode.

In the novel silicon-based heterojunction solar cell of the present invention, a P-type heavily doped amorphous silicon layer and an ultra-thin intrinsic amorphous silicon layer are contained between the transparent conductive film and the P-type nano-silicon layer.

In the above-mentioned novel silicon-based heterojunction solar cell of the present invention, the thickness of the transparent conductive film ITO is 60-100 nm; the thickness of the intrinsic amorphous silicon layer is 1-5 nm; the thickness of the P-type heavily doped amorphous silicon layer is 3 nm. ~10nm; the thickness of the P-type nano-silicon layer is 5-15nm; the thickness of the intrinsic amorphous silicon layer is 3-10nm; the thickness of the N-type silicon wafer is 200-300μm, and the resistivity is 1-10Ω.cm; The thickness of the electrode is 1-5 μm.

Subsequent examples will prove that, compared with traditional silicon solar cells, the novel silicon substrate heterojunction solar cell of the present invention is a representative of a new generation of solar cells, which can obtain lower cost and higher photoelectric conversion than ordinary silicon solar cells Efficiency: Better long-term use stability and higher conversion efficiency than ordinary amorphous silicon solar cells, this new silicon-based heterojunction solar cell was prepared under the standard simulated light intensity of AM1.5, 100mW/ ^cm2 The efficiency reached 17.2%.

Description of drawings

Fig. 1 is a schematic diagram of a silicon substrate heterojunction solar structure according to the present invention.

Among them: 1 is the Ag grid line electrode; 2 is the transparent conductive film (ITO); 3 is the intrinsic amorphous silicon layer (ia-Si:H); 4 is the P-type heavily doped amorphous silicon layer (p ⁺ - a-Si:H); 5 is the P-type nano silicon layer (p-nc-Si:H); 6 is the intrinsic amorphous silicon layer (ia-Si:H); 7 is the N-type silicon substrate; 8 is Ag metal back electrode.

Detailed ways

The present invention will be further elaborated below in conjunction with the accompanying drawings and specific embodiments. These examples should be understood as only for illustrating the present invention but not for limiting the protection scope of the present invention. After reading the contents of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

As shown in Figure 1, each layer structure of the novel silicon-based heterojunction solar cell provided by the preferred embodiment of the present invention utilizes screen printing of a layer of low-temperature silver paste to form the front grid electrode; magnetron sputtering grows an ITO film 60- 100nm; PECVD deposits intrinsic amorphous silicon (ia-Si:H) with a thickness of 1-5nm; deposits P-type heavily doped amorphous silicon (p ⁺ -a-Si:H) with a thickness of 3-10nm; Deposit P-type nano-silicon (p-nc-Si:H) with a thickness of 5-15nm; deposit intrinsic amorphous silicon (ia-Si:H) with a thickness of 3-10nm; N-type silicon wafer with a thickness of 200-200nm 300μm, resistivity 1~10Ω.cm; evaporated Ag back electrode, thickness 1~5μm. The specific preparation process is:

(1) Cleaning process: the silicon wafer is first cleaned with RCA, and then the surface oxide layer is removed with a dilute hydrofluoric acid solution, so that the surface of the silicon wafer is free from spots, scratches, and the surface is completely dehydrated, and finally rinsed with a large amount of deionized water. The cleanliness of the chip surface is very high.

(2) PECVD process: Intrinsic amorphous silicon (ia-Si:H), P-type nano-silicon (p-nc-Si:H), and P-type heavily doped amorphous silicon (p ⁺ -a-Si:H), intrinsic amorphous silicon (ia-Si:H) between P ⁺ /ITO, the deposition temperature should be around 200°C.

(3) Magnetron sputtering process: use magnetron sputtering technology to sputter a layer of ITO film 60-100nm, the temperature is about 100 ℃.

(4) Screen printing and sintering process: Print low-temperature silver paste on the ITO film with a screen printing machine to form grid lines, and then sinter electrodes at low temperature, and the temperature is controlled at about 100°C.

example

As shown in FIG. 1 , the silicon substrate 7 is an N-type Czochralski monocrystalline silicon wafer with a crystal orientation of <100> and a resistivity of 2Ω·cm, polished on one side, and a thickness of 260 μm. The thickness of the ITO film 2 grown by magnetron sputtering is 80nm; the thickness of the intrinsic amorphous silicon film 3 deposited by PECVD is 2nm; the thickness of the deposited P-type heavily doped amorphous silicon film 4 is 5nm; the deposited P-type nano-silicon film The thickness of 5 is 12 nm; the thickness of deposited intrinsic amorphous silicon film 6 is 3 nm; the thickness of evaporated Ag back electrode 8 is 3 μm.

It has been determined that under the irradiation of the simulated light source AM1.5 and the standard light intensity of 100mW/cm ² , the efficiency of the novel silicon-based heterojunction solar cell prepared in this example reaches 17.2%, and the effective area of the cell is 0.28cm ² , where The open circuit voltage is 602mV, the short circuit current density is 36.5mA/cm ² , and the fill factor is 0.783.

Claims (3)

1. A novel silicon substrate heterojunction solar cell is characterized in that it comprises Ag grid line electrodes (1), transparent conductive film (2), intrinsic amorphous silicon layer (3), P-type heavily doped Amorphous silicon layer (4), P-type nano-silicon layer (5), intrinsic amorphous silicon layer (6), N-type silicon substrate (7) and Ag metal back electrode (8), wherein: The Ag grid line electrode (1) is located on the transparent conductive film ITO (2) as the front-side lead-out electrode; A transparent conductive film (2) is located on the intrinsic amorphous silicon layer (3) as a front electrode; The intrinsic amorphous silicon layer (3) is located on the P-type heavily doped amorphous silicon layer (4); The P-type heavily doped amorphous silicon layer (4) is located on the P-type nano-silicon layer (5); The P-type nano-silicon layer (5) is located on the intrinsic amorphous silicon layer (6) and the N-type silicon substrate (7); The intrinsic amorphous silicon layer (6) is located on the N-type silicon substrate (7); The N-type silicon substrate (7) is located on the Ag metal back electrode (8) as the base area of the solar cell; The Ag metal back electrode (8) is used as the back lead-out electrode. 2. by the novel silicon substrate heterojunction solar cell described in claim 1, it is characterized in that, contain the amorphous silicon layer ( 4) and an ultra-thin intrinsic amorphous silicon layer (3). 3. The novel silicon-based heterojunction solar cell according to claim 1 or 2, characterized in that the thickness of the transparent conductive film ITO (2) is 60-100 nm; the thickness of the intrinsic amorphous silicon layer (3) is 1-5nm; the thickness of the P-type heavily doped amorphous silicon layer (4) is 3-10nm; the thickness of the P-type nano-silicon layer (5) is 5-15nm; the thickness of the intrinsic amorphous silicon layer (6) is 3-10 nm; the thickness of the N-type silicon wafer (7) is 200-300 μm, and the resistivity is 1-10 Ω·cm; the thickness of the Ag back electrode (8) is 1-5 μm.

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